1. Field of the Invention
This invention relates to display systems, and in particular, to cathode ray tube (CRT) display systems.
2. Description of Related Art
Conventionally, cathode ray tubes (CRTs) have been used to produce high quality video displays. CRT screens are projection devices typically comprising an electron gun assembly directed at a phosphor-coated screen and circuitry to control the path of the emitted electrons. In a typical color CRT display, the electron gun assembly has three electron guns, with each gun assigned to a different one of the three primary colors, red (R), green (G), and blue (B). Electrons from the cathodes are accelerated in a vacuum from the cathodes to the screen. At the screen, the electrons excite the phosphors to generate a light output.
In a typical CRT, the cathode at one end of the CRT emits a beam of electrons towards the anode through a grid. After passing through the anode, the electron beam is focused and deflected toward a desired area of the screen. The screen has a pattern of RGB phosphor stripes, which emit light when struck with electrons to produce the desired color output. The electron beam is typically scanned raster style across portions of the screen to create the desired visual image. The electrons travel from the photocathode to the phosphor through a vacuum, which is formed by separating the cathode from the screen by some distance and sealing the vacuum, such as by frit sealing.
One way of altering the motion of electrons to a desired location on the screen is by passing the electron beam through a magnetic field. The magnetic fields can be generated by passing current through relatively high inductance yoke coils, usually placed around the outside of the neck of the CRT. Although this method can be made to operate from low voltage power supplies, the current levels required by the yoke coils increase the amount of power required by the CRT display system. The inductance of the yoke coils also places an upper limit on the frequencies which can be used to drive them. Consequently, even though the electromagnetically deflected tube offers the advantages of good focus and can be driven by low voltage deflection circuitry, it also increases the weight and power requirements of the system.
In addition, CRT screens are limited in size due to the requirement that the electrons must travel in a vacuum. Much of the weight and bulk of a CRT is due to the heavy walls containing the vacuum. As the size of the screen increases, the walls necessarily become heavier and thicker. There comes a point where it is not economically or mechanically feasible to make a large CRT screen. Typically, 50-inch diagonal screens are the largest CRT displays commercially practicable.
Accordingly, a display system is desired that overcomes the deficiencies described above of conventional display systems.
In accordance with the invention, a cathode ray tube (CRT) display system is provided utilizing a matrix of addressable carbon nanotubes covered by a pattern of phosphor. The nanotubes can be addressed or selected individually, corresponding to the picture being reproduced on the CRT. Rear projection type electron guns, in conjunction with the addressable nanotube matrix, eliminates the need for a deflection yoke, thereby reducing both the size and weight of the CRT display.
According to one embodiment, red (R), green (G), blue (B) rear projection electron guns direct scanning electron beams, within a vacuum enclosure, to the nanotube matrix. The electron beams have varying intensity according to the picture to be reproduced. In conjunction with the electron beam scanning, nanotubes on the matrix are selected, also according to the picture to be reproduced. Selected nanotubes turn on and, acting as an accelerating electrode, help draw the desired electron beams from the RGB electron guns to the desired portions of the nanotube matrix. Upon striking the phosphor overlying the selected nanotube, the phosphor emits the desired light, resulting in a re-created visual image. The addition of the addressable nanotube matrix eliminates the need for a large magnetic deflection yoke. Thus, the CRT display according to the present invention is smaller and lighter than conventional CRT displays and requires less energy consumption.
The present invention will be more fully understood upon consideration of the detailed-description below, taken together with the accompanying drawings.